Purification of anthraquinone



Patented Feb. 16, 1932 Mrs!) STATES PATENT OFFICE ALPHONS O. JAEGER, OFC R AFTONQPENNSYLVANIA, ASSIGNOR TO THE SELDEN COM- IPANY, OFPITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE No Drawing.

PURIFICATION or ANTHRAQUINONE of the products obtained in succeedingoperations. Particularly itis necessary to remove any carbazole orphenanthrene oxidation products present. 1

According to the present invention crude anthraquinone is subjected toone or more treatments with solvents, at least one of which contains aheterocyclic compound. Various types of liquid heterocyclic compoundsmay be used such as those containing sulfur, such as, for examplethiophene, its homologues and their liquid derivatives; those containingnitrogen, such as pyrrol, its homologues and derivatives; quinoline, itshomologues and derivatives; and pyridine together with its homologuesand derivatives. The preferred heterocyclic compounds are thosecontaining the furane nucleus:

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such as furane and alkyl furanes, furfural and its homologues,furfurylalcoholand. esters of furoic acid. Solventscontaining compounds with ahydrogenated furane nucleous, such as tetrahydrofurfuryl alcohol mayalso be used, and it should be understcod 'that throughout thespecification the term furane body will b'e'used to cover not only thecompounds which contain the actual furane nucleus but also those whichcontain the hydrogenated furane nucleus. Solvents containing furanebodies show a very high solvent power in the cold for carbazole andphenanthrene and most of the other impurities present in crudeanthraquinone, but they show a remarkably low solvent power in the coldfor anthraquinone itself and are, therefore, excellently suited for thepurification Application filed August 1. 1923. .Serial No. 296,869.

of crude anthraquinone. While the desirable solvent properties areshared in a greater or less degree by all of thefurane bodies, thefurfurals are themost eiiicient and be-' cause of their low price may beconsidered the preferred solvents. Their high boiling point reduceslosses and gives a greater temperature range for recrystallization andthus ,makes them preferable to the furanes themselves,which arerelatively low boiling Fur-' furyl and tetrahydrofurfuryl alcoholpossess hlgh boiling points and good solvent powers, but areopen to thedisadvantage that they are miscible with water. The furfurals, however,possess all of the good qualities of the other furane bodies with aminimum of undesirable qualities.

Not only are the solvents containing furane bodies advantageous becauseof their vary great solvent efficiency and low cost of the preferredmembers, such as the furfurals, but

.they are all relatively non-toxic and possess odors which are notunpleasant, a very important advantage when they are compared, forexample, with pyridine, which, while an effective solvent, possesses amost unpleasant odor, whichconstitutes a serious nuisance and greatlyrestricts its use. I

In. carrying out the present invention, crude'anthraquinone may besubjected to a single treatment, either recrystallization, washing orleaching with a solvent containing a heterocyclic compound andpreferably a furane body,-'or, in some cases, particularly when the.anthraquinone contains a large amount ofimpurities, it is desirable tosubject it "to two 'or more treatments, which may be with the same or-with different solvents. Thus, for example, it is desirable in somecases to treat with a solvent for phenanthrene and its derivatives, suchas, for example, alcohol, gasoline, acetone, aromatic hydrocarbons, suchas benzene, toluene, solvent naphtha, and the like, halogenated aromaticcompounds, particularly orthodichlor-benzene' or the chlorinatedvresidues from the chlorine purification of light oils, which containmany chlorinated aliphatic compounds as well as chlorinated alicycliccompounds. The treatments may be successive or a mixed solvent may beused in which one or more heterocyclic compounds, such as furane bodies,are associated with other solvents. When a plurality of solventtreatments are used they may be 5 in any order, but preferably the lasttreatment should be with a solvent containing a heterocyclic compoundand preferably a furane body in order to produce anthraquinone with thehighest purity.

The invention will be described in connection with specific examples,which illustrate a few typical modifications. It should be understood,however, that the invention is in no sense limited to the details of theprocedure therein set forth.

1 7 Example 1 100 'parts of a dark brown, oily, crude anthraquinone,obtained by the catalytic oxida- 3 tion of 29-31% crude anthracene witha vanadium catalyst and containing about 74.4% of anthraquinone, isheated to about 110 C. with 500 parts of furfural, methylfurfural, or amixture of the two. The undissolved material is filtered off and the hotsolution is permitted to cool; Anthraquinone separates out on cooling,and is filtered off.

' The undissolved solids amount to about 38.4 parts, and when analyzedby the Hoechst method constitute anthraquinone of 95.2%

. alcohol, and the like, may be used. The furfurals, however, givesomewhat better results, and because of their lower p'rice present adistinct economic advantage. Other liquid .heterocyclic compounds, suchas pyridine, pyrrol, thiophene and their homologues or derivatives maybe used instead of solvents containing 'furane bodies and they givesimilar results but in the case of pyridine they are open to the seriousdisadvantage entailed in the vile odor of the solvent.

Instead'of using an impure anthraquinone which has been'obtained bythecatalytic oxi dation of crude anthracene, a different type of impureanthraquinone, prepared by chro- F mic acid oxidation, may be purifiedin the same way. A high grade product is obtained, since the mainimpurities, such as hydrocarbons and their oxidation products, nitrogen"ou's bases, as carbazole, phenanthrene, phenanthraquinone and dead oilsare readily carbazole as part of its impurities. marked solvent actionof heterocyclic comsoluble in the solvents containing heterocycliccompounds.

Instead of recrystallizing the crude anthraquinone by treatment with hotfurfural and cooling, it may be leached by washing with furfural orother solvents containing heterocyclic compounds, or by washing with amixture of a solvent containing one or more heterocyclic compounds, suchas furane bodies, and other solvents, such as benzol, toluol, solventnaphtha, gasoline, acetone, chlorinated hydrocarbons, such aschlorbenzene, orthodichlorbenzene, or the residue from thechlorine-purification of light oil. A mixture of the solvents may beused for leaching, or, first one may be used and then the other, but itis preferable-to use the solvent containing furfural or otherheterocyclic compounds as the last solvent because of its high solventaction on carbazole and the other impurities.

Emamplc 2 I 100 parts of the oily tailings from the catalytic oxidationof anthraquinone,and con taining about 80.36% anthraquinone, are washedwith up to 200 parts of a caustic soda solution in order toremoveorganic acids such as phthalic acid, benzoic acid, maleic acid andother acids of indeterminate constitution. The product is then dried andheated up to 100'120' with 1,000 parts of pure or technical furfural orpyridine or a mixture. The mixture is allowed to cool to roomtemperature, and the anthraquinone which precipitates out is filtered01f.

80'parts of the purified anthraquinone are obtained, which, whenanalyzed by the Hoechst method, show a purity of 98.46%. Theanthraquinone recovered, therefore, is about 97.9% of the anthraquinonecontent of the original crude material. The product when worked up intoalizarin gives a good shade. If the product is sublimed by the standardsublimation methods an anthraquinone of 99.9% purity is obtained Itshould be noted that this crude anthraquinone normally contains about 5%of The pounds on carbazole is clearly illustrated in the practicallycomplete removal effected by the recrystallization. I

. Example 3 Various grades of crude anthraquinone are washed withbenzol, toluol, solvent naphtha,

acetone, gasoline, alcohol, orthodichlorbenzene or other chlorinatedsolventsin orderto remove oils and hydrocarbons such as phenanthrene. Asemi-purified anthraquinone of 92 to 94% purity is obtained in thismatter, and is then washed with five to eight times its weight offurfural or pyridine at room temperature, or at a somewhat elevatedtemperature. After washing with furfural it is again washed with a smallamount of one of the solvents used in the first treatment in order todisplace a maximum of furfural from the anthraquinone cake, since thesolvents used in the first process are for the most part cheaper, and insome cases very much cheaper, than furfural and especially pyridine, andthe loss of the more expensive furfural or much more expensive pyridineis thereby reduced to a minimum. The resulting anthraquinone shows apurity of 98 to 98.8%, and can be transformed into 99.6 to 99.9% pureanthraquinone by sublimation. The recovery is from 85 to 90%, based onthe anthraquinone content of the crude material.

What is claimed as new is:

1. A method of purifying impure anthraquinone, which comprisessubjecting it to the action of at least one solvent containing at leastone furane body in amounts sufficient to cause a substantial separationof the anthraquinone from impurities.

2. A method of purifying impure anthraquinone, which comprisessubjecting it to the action of at least one solvent containing furfuralin amounts sulficient to cause a substantial separation of theanthraquinone from impurities.

3. A method of purifying impure anthraquinone from the catalyticoxidation of impure anthracene which comprises subjecting it to theaction of at least one solvent containing at least one furane body inamounts sulficient to cause a substantial separation of theanthraquinone from impurities.

4:. A method of purifying impure anthraquinone from the catalyticoxidation of impure anthracene, which comprises subjecting it to theaction of at least one solvent containing furfural in amounts suliicientto cause a substantial separation of the anthraquinone from impurities.

5. A method according to claim 1, in which at least one treatment with asolvent containing a furane body consists in a recrystallization fromthe solvent.

6. A method according to claim 2, in which at least one treatment with asolvent containing furfural consists in a recrystallization from thesolvent.

7 A method of purifying impure anthraquinone, which comprises subjectingit to at least one treatment with a solvent consisting substantially offurane bodies in amounts sufficient to cause a substantial separation ofthe anthraquinone from impurities.

8. A method of purifying impure anthraquinone which comprises subjectingit to at least one treatment with a solvent consisting substantially offurfural in amounts sufficient to cause a substantial separation of theanthraquinone from impurities.

9. A method of purifying impure anthraquinone produced by the catalyticvapor 11. A method of purifying impure anthra-' quinone, which comprisessubjecting it to the action of at least one furfural and at least onenon-heterocyclic compound which possesses high solvent power forphenanthrene and its oxidation products in amounts sufiicient to cause asubstantial separation of the anthraquinone from impurities. SignedatPittsburgh, Pennsylvania, this 26th day of July, 1928.

ALPHONS O. JAEGER.

